Power converters are indispensable devices in electrical platforms and systems such as computing platforms, communication and mobile systems, medical systems, electric vehicles, military systems, renewable energy systems, aerospace systems, and almost all peripherals and devices. These systems and related applications impact people's daily life. New technology for power electronics and power converters is critical for achieving higher energy efficiency and significant cost reduction and size.
Power converters convert voltage or current from one level to another and/or from one form to another in order to supply energy to a specific load. Such power converters are of several types, such as DC-DC power converters, AC-DC power converters, DC-AC power inverters, and AC-AC power inverters.
Switching DC-DC power converters have the advantage of much higher energy efficiency as compared with converters using linear regulators. However, the switching DC-DC power converter is generally larger than the linear regulator converter primarily because it typically requires power inductors, power transformers, more switching power devices and control circuits. Nonetheless, the switching DC-DC power converters are widely used especially when the energy efficiency is crucial.
In general, the integration and size reduction of other technologies, such as Integrated Circuits (ICs) for microprocessors and other general purpose processors (e.g., graphic ICs and communications ICs), are advancing at a faster pace than switching power converter technologies. Integrating power converters “on chip” yields several advantages such as smaller size, lighter weight, reduced distribution, reduced distribution losses, and potentially reduced EMI (Electromagnetic Interference).
When the dimensions of solid materials are reduced to nanometer size, the materials often exhibit new and interesting behavior which can constitute the basis for a new generation of electronic devices. Hence, nanotechnology helps to achieve reliable nanometer-scale power devices with small footprints and reduced power consumptions. Consequently, there is a need to develop new nanotechnology-based power devices that can result in transformative advances.
A DC-DC switching power converter typically comprises switching power devices such as MOSFETs (Metal Oxide Field Effect Transistor), analog and/or digital control circuits filter capacitors, power inductors, and sometimes power transformers. Switching power devices and control circuits can be easily integrated on a single chip, but the power inductors, transformers and capacitors are often bulky and difficult to integrate with other components. In most cases, such off-chip components are an obstacle for reducing the size of switching power converters.
For many electronic systems, it is desirable to develop integrated DC-DC power converters for System on Chip (SoC) applications. The most common approaches to integrate power converters include: Power System in Package (PSiP) and Power System on Chip (PSoC). PSiP uses off-the-shelf components in order to supply large power requirements, but such components often limit size reduction. PSoC often integrates components, such as power inductors and capacitors, directly on IC (Integrated Circuit) chips. Such an approach can minimize size by taking advantages of known micro-fabrication technologies. Carbon nanotubes (CNTs) at the nanometer scale have sometimes been used to form electrical components. However, there are interfacial resistance problems associated with conventional connectors, such as copper traces on a substrate, that are often used to couple CNT components of a converter.
Therefore, if the connection problem can be diminished or removed, it appears to be advantageous to replace conventional technology with nanotechnology to achieve reliable nanometer-scale power devices with smaller footprints and less power consumption. Scaling the components to nanometer size helps to reduce converter size. Nanotechnolgy power components would provide for high-density on-chip integration of the power converters resulting in optimum power management, elimination of discrete component, smaller footprint, lower distribution losses, and lower parasitic delays.